Stabilizing solution of tetra-alkyl lead compounds



Patented Sept. 15, 1942 STABILIZING SOLUTION 0F TETRA-ALKYL LEADCODI'POUNDS Troy Lee Cantrell, Lansdowne, and Carlton Louis Suplee,Malvern, Pa., assignors to Gulf Oil Corporation, Pittsburgh, Pa., acorporation of Pennsylvania No Drawing. Application February 27, 1940,Serial No. 321,132

6 Claims.

This invention relates to stabilizing solutions of tetra-alkyl leadcompounds; and it comprises a method of stabilizing liquids containingsuch compounds, particularly ethyl gasoline, to inhibit the developmentof a hazy appearance, wherein small quantities of certain amino salts offatty acids are added'to such liquids; and it also comprises as ananti-knock motor fuel stable to light, a gasoline containing atetra-alkyl lead compound and a small quantity of such an amino salt ofa fatty acid; all as more fully hereinafter set forth and as claimed.

It is customary in the production of so-called ethyl gasoline'f to add asmall amount of a tetra-alkyl lead compound, usually tetra-ethyl lead,to a good grade of gasoline to reduce knocking in high compressiongasoline engines. The amountof tetra-alkyl lead compound added to agasoline depends upon the nature of the gasoline and the desiredanti-knock rating. Tetra-ethyl lead is customarily added to the gasolinein the "form of a liquid preparation called ethyl fluid," which usuallyis a solution containing a mixture of tetra-ethyl lead, alkylenedi-halide (e. g. ethylene di-bromide or ethylene di-chloride or both).Usually a small amount of a dye' is also added to impart a distinctivecolor; addition being either to the fluid or to the gasoline. The ethylfluid is added to the gasoline in a quantity sufiicient to produce thedesired anti-knock rating. In some cases only a relatively small amountis added, but sometimes, as with certain aviation grades of gasoline, alarge amount is used. Gasoline to which a large amount of tetra-ethyl orother tetra-alkyl lead has been added is often referred to as a heavilyleaded gasoline.

Although tetra-alkyl lead compounds, and in particular tetra-ethyl lead,are particularly efficient for imparting anti-knock properties togasoline, their employment is not entirely free from disadvantage. Forone thing, leaded gasoline tends to develop a hazy appearance uponstanding, particularly in strong sunlight. In direct sunlight in thesummer time, any ethyl gasoline 4 may develop a perceptible hazinessafter an hour or two of exposure, and longer periods of exposure mayresult in a very marked haziness. Precipitation finally occurs. Thishazing phenomenon is also sometimes observed in the ethyl fluid itself.

The formation of haze in gasoline is objectionable. Customers prefer aproduct which is clear and transparent; free from haze or muddiness. Afurther and perhaps more important objecgasoline often develops withhaze formation. Also, damage is likely to occur in the fuel lines andcarbureter. The development of haze in ethyl fluid itself is alsoobjectionable, because when a hazy ethyl fluid is blended with gasolineto form ethyl gasoline, the haze is at once introduced into the fuelwith all its attendant disadvantages.

An object achieved by this invention is to achieve a stabilizationagainst haze formation in liquids containing tetra-alkyl lead compounds,such as ethyl fluid and ethyl gasoline.

We have found that haze formation in solutions of tetra-alkyl leadcompounds, such as ethyl fluid and ethyl gasolines, can be retarded orobviated by incorporating in such solutions small quantities,proportioned on the amount of tetra-alkyl lead in solution, of salts orsoaps formed by fatty acids higher than acetic acid.

with cycloaliphatic amines or with the aliphatic amines higher than themethyl amines.

' These higher amino salts of higher fatty acids 7 may be added withadvantage to liquids containing tetra-alkyl lead compounds generally.They are particularly advantageous in stabilizing moderately leadedgasolines such as ordinary ethyl gasoline of automobile grades. However,they effect a stabilization of even heavily leaded grades of gasoline,such as certain aviation grades of gasoline. The salts being soluble ingasoline and the like, the manner of incorporating them in solutions oftetra alkyl lead compounds is not critical. For example they may beincorporated in ethyl fluid at any stage during the preparation thereofor they may be incorporated in gasoline, prior to the addition of ethylfluid, along with the ethyl fluid, or subsequent to blending the ethylfluid with the gasoline.

Even very small proportions of these salts arev sumcient to exert asubstantial stabilizing effect against light in fluids containing.tetra-alkyl lead compounds. In practically all cases an addition offrom 3 to 80 pounds of salt per 1000 barrels of gasoline containing from0.01 to 1.0 per cent by weight of tetra ethyl lead exerts a markedstabilizing'efiect against light; to produce an ethyl gasoline stable tolight under the usual conditions of exposure. In general, commercialethyl gasoline containing from 0.02 to 0.40 per cent by tion is that areduction in the octane rating of 55 weight of tetra-ethyl lead requiresonly about 5 to about 30 poundsof these amino salts of fatty acids perbarrel of gasoline to produce a satisfactorily stabilized product withordinary conditions of storage and handling. Mostly 5 to 20 pounds ofsuch salts per 1000 barrels of gasoline carrying from 0.02 to 0.40 percent of tetra-ethyl lead suflices. However, as there is some variance inthe stabilizing power of the difl'erent salts, the amounts to be addedvary accordingly.

The application of the higher amino salts of higher fatty acids to thestabilization of solutions of tetra-alkyl lead compounds against hazeformation is not limited to leaded gasoline, but they may beincorporated directly in the ethyl fluid or concentrate" with advantage.When these salts are incorporated in the tetra-alkyl lead concentrate,they stabilize it during storage and shipment, and a concentratecontaining such a salt can then be added to gasoline to impart theretoboth anti-knock properties and resistance to hazeformation. Ordinarilythe proportion of salt added .to ethyl fluid is somewhat greater than isrequired for its stabilization so that by the addition of the usualsmall amount of ethyl fluid to the gasoline a suitablestabilizing amountof the salt will be incorporated in the gasoline. Generally from 1 to 10per cent by weight, based on the tetra-ethyl lead, of a higher aminosalt of a higher fatty acid stabilizes commercial tetraethyl leadconcentrates, such as ethyl fluid, and on adding the stabilizedconcentrate to gasoline to produce ethyl gasoline, a satisfactorystabilized ethyl gasoline is obtained.

A large variety of amino salts of fatty acids may be advantageouslyemployed to stabilize solutions of tetra-alkyl lead compounds againsthaze formation. However, we have found that there is a considerablevariance in the stabilizing potencies of these salts. Thus we have foundthat the amino salts of acetic acid, and the fatty acid salts of themethyl amines (mono-, diand trimethyl amines) do not constitute whollysatis-- factory stabilizers for ethyl fluid, ethyl gasoline and thelike. However, salts formed by fatty acids higher than acetic acid withaliphatic amines higher than the methyl amines (i. e., amines containingat least one alkyl group higher than the methyl group) or withcycloaliphatic amines do constitute satisfactory stabilizers. Of thesehigher amino salts of higher fatty acids we have found that thosecontaining large hydrocarbon radicals are more eflective stabilizersthan those containing only small hydrocarbon radicals. For example,butylamine laurate, cyclohexylamine oleate and amyl cyclohexyl aminestearate constitute more effective stabilizers than ethylaminepropionate. The higher compounds have a greater solubility in gasoline.

We have found, moreover, that the aliphatic amines higher than themethyl amines, and the cycloaliphatic amines form more effective sta-'bilizers with fatty acids than do the aromatic amines, such as anilineand the naphthylamines. This may be due to the low basicity of thearomatic amines as compared with the aliphatic and cycloalipathicamines. The ionization constants of the aromatic amines are of the order10 The higher aliphatic and the cycloaliphatic amines, 'on the otherhand, have ionization con-- stants of the order of 10-- to i; e. theyare much stronger bases.

The secondary amines such as di-butylamine, di-cyclohexylamine and amylcyclohexyl amine are best adapted for the present purposes. Oleic andstearic acid are particularly effective fatty acids, and of the two,oleic is the more effective.

The oleates, stearates and laurates of di-cyclohexylamine and amylcyclohexyl amine are particularly useful stabilizers because of theirhigh inhibiting power. From 5 to 20 pounds of .these salts per 1000barrels of ethyl gasoline containing 0.02 to 0.40 per cent by weight oftetra-ethyl lead produces a gasoline which is perfectly bright after 5hours exposure to bright sunlight. Also, they are only slightly solublein water; less so than most of the other amine-fatty acid salts. Ethylfluid and ethyl gasoline containing them are less damaged on contactwith water.

Many other salts, however, are .also satisfactory, for example,butylamine and di-butylamine oleates, amylamlne oleate, di-butylaminestearate, cyclohexylamine oleate, benzylamine oleate, N-phenylcyclohexylamine oleate, and piperidine oleate.

It is an advantageous property of many of the higher amine-higher fattyacid salts that they are liquid or semi-liquid in character and henceare readily blended with gasoline, ethyl fluid and the like. They arefreely mixable.

Besides individual amines and individual fatty acids, mixtures of aminesand of fatty acids may be used in forming the stabilizers of thisinvention. Thus,commercial mixtures of fatty acids derived from theordinary fatty oils, such as coconut oil, may be employed in place of asingle fatty acid such as oleic acid.

A particular advantage of the stabilizers used in this invention istheir cheapness and ease of production. The source materials-amines andfatty acids-are in many cases available in large quantities at very lowcost. The method of manufacture of the salts therefrom consists merelyof mixing the ingredients and sometimes heating the mixture during thereaction.

The stabilizing salts used in this invention also have other propertieswhich make them desirable. They do not injuriously aflect the oxygenstability of gasoline or promote gum formation therein. Samples ofcracked ethyl gasoline containing these amine-fatty acid salts have beenaged and tested for oxygen stability and by the copper dish method forgum formation. The presence of the salts did not promote either oxygeninstability or gum formation. The salts are non-corrosive to commonpackaging materials such as steel, zinc, copper and tin, and arecompatible with the dyes commonly used in ethyl gasoline. All of themare sufficiently soluble in gasoline to accomplish the intendedstabilization. Continued storage of gasoline containing these salts doesnot affect their stabilizing properties.

The following specific examples will serve to illustrate the excellenthaze-inhibiting properties of the higher amine-higher fatty acid salts;Example 1.-Ethyl gasoline containing 0.1 per cent by weight .oftetra-ethyl lead (added in the form of ethyl fluid comprisingtetra-ethyl lead, ethylene dibromide, ethylene dichloride, and a dye)was treated with butylamine oleate in the proportion of 10 pounds of thelatter per 1000 barrels of gasoline. exposed for 5 hours to sunlight andthe appearance of the gasoline was noted. At the end of the 5-hourexposure no haziness whatever could be observed. In contrast to thisresult, a sample of the same ethyl gasoline, exposed under identicalconditions but containing no inhibitor, showed a large degree ofhaziness at the end of the 5-hour period, and a heavy precipitateresulted.

Example 2 .Benzylamine oleate, N-phenyl cyclohexyl amine oleate anddi-butylamlne stearate were tested in the same amounts and The resultingmixture was The results obtained with them were satisfactory.

Benzylamine oleate, the least potent of the threestabilizers, stabilizedethyl gasoline to such a point that at the end of the -hour exposure tosunlight only a small degree of haziness was observed, whereas theunstabilized gasoline developed a heavyprecipitate.

Example 3.-Di-cyclohexylamine oleate, amyl cyclohexyl amine oleate anddi-cyclohexylamine stearate were tested in a manner identical with thatof Example 1. In each case, at the end of I the 5-hour exposure tosunlight no haziness whatever was noted; the ethyl gasoline wasperfectly bright and clear.

While our invention has been described herein with reference toparticular embodiments and specific examples thereof, we do not intendthat our invention shall be limited to such embodiments and examplesexcept as hereinafter defined in the appended claims.

What we claim is:

1. A method of stabilizing a solution of a tetra-alkyl lead compoundagainst haze formation, which comprises incorporating in said solutionan amine salt of a fatty acid, in an amount, proportioned on the amountof tetra-alkyl lead present, suflicient to inhibit haze formation due tothe presence of said amount of tetra-alkyl lead, said amine salt being asalt of a secondary amine selected from the group consisting ofdibutylamine, di-cyclohexylamine and amyl cyclohexyl amine and a fattyacid selected from the group consisting of oleic, stearic and lauricacids.

2. A method of stabilizing a motor fuel containing about 0.01 to 1.0 percent of tetra-alkyl lead against haze formation, which comprisesincorporating in said motor fuel di-butylamine oleate in an amountbetween 3 and 80 pounds per 1000 barrels, sufficient to inhibit hazeformation due to the presence of said amount of tetraalkyl lead.

3. A method of stabilizing a motor fuel containing about 0.01 to 1.0 percent of tetra-alkyl lead against haze formation, which comprisesincorporating in said motor fuel di-cyclohexylamine oleate in an amountbetween 3 and 0 pounds per 1000 barrels, sufiicient to inhibit hazeformation due to the presence of said amount of tetra-alkyl lead.

4. As an improved anti-knock motor fuel stable to light, a gasolinecontaining a tetra-alkyl lead compound in amount suflicient to impartantiknock properties to said gasoline and an amine salt of a fatty acidin amount suflicient to inhibit haze formation due to the presence ofsaid amount of tetra-alkyl lead, said amine salt be-' ing a salt of asecondary amine selected from the group consisting of. di-butylamine,di-cyclohexylamine and amyl cyclohexyl amine and a fatty acid selectedfrom the group consisting of oleic, stearic and lauric acids.

5. As an improved anti-knock motor fuel stable to light, a gasolinecontaining about 0.01 to 1.0 per cent of tetra-alkyl lead anddibutylamine oleate in an amount between 3 and pounds per 1000 barrels,sufiicient to inhibit haze formation due to the presence of said amountof tetra-alkyl lead.

6. As an improved anti-knock motor fuel stable to light, a gasolinecontaining about 0.01 to 1.0 per cent of tetra-alkyl lead anddi-cyclohexylamine oleate in an amount between 3 and 80 pounds per 1000barrels, suflicient to inhibit haze formation due to the presence ofsaid amount of tetra-alkyl lead.

, TROY LEE CANTREEL.

CARLTQN L. SUPLEE.

